ABSTRACT
@#Introduction: Metal artifacts can degrade the image quality of computed tomography (CT) images which lead to errors in diagnosis. This study aims to evaluate the performance of Laplace interpolation (LI) method for metal artifacts reduction (MAR) in CT images in comparison with cubic spline (CS) interpolation. Methods: In this study, the proposed MAR algorithm was developed using MATLAB platform. Firstly, the virtual sinogram was acquired from CT image using Radon transform function. Then, dual-adaptive thresholding detected and segmented the metal part within the CT sinogram. Performance of the two interpolation methods to replace the missing part of segmented sinogram were evaluated. The interpolated sinogram was reconstructed, prior to image fusion to obtain the final corrected image. The qualitative and quantitative evaluations were performed on the corrected CT images (both phantom and clinical images) to evaluate the effectiveness of the proposed MAR technique. Results: From the findings, LI method had successfully replaced the missing data on both simple and complex thresholded sinogram as compared to CS method (p-value = 0.17). The artifact index was significantly reduced by LI method (p-value = 0.02). For qualitative analysis, the mean scores by radiologists for LI-corrected images were higher than original image and CS-corrected images. Conclusion: In conclusion, LI method for MAR produced better results as compared to CS interpolation method, as it worked more effective by successfully interpolated all the missing data within sinogram in most of the CT images.
ABSTRACT
Abstract@#Introduction: Computed tomography (CT) has been widely used for postoperative spine assessment. However, the effectiveness of CT is limited by the presence of multiple artefacts surrounding metal implants. An artefact causes degradation of image quality and obscures the interpretation of spine CT images by a radiologist. The purpose of this study was to evaluate the optimum angle of gantry tilt and metal rod placement which produced the least metal artefact on CT images. Methods: A customised phantom was developed with different transverse angles of metal placement. The transverse angles of metal placement inside the phantom varied at 20°, 30°, 40° and 45°. The phantom was scanned with CT scanner at 0° axial scan angle. It was followed by acquisitions at different gantry tilt angles ranging from −12° to 20°. Quantitative and qualitative assessment by determining the signal-to-noise ratios (SNRs) of the CT images was performed. Results: The severity of the metal streak artefact increased as the metal insertion angles became wider up to 45° due to the widespread of streaking area. The severity of artefacts was reduced with the increment of the gantry tilt angle, which was observed in images acquired at 20°. Conclusion: For the gantry tilt angulation technique, the optimum gantry angle for metal artefact reduction is at the widest angle, which is +20° angulation. Although the gantry tilt technique did not eliminate the metal artefacts, it enabled a significant reduction of metal artefacts and improved image quality.